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Fwd = Laser Search for Extraterrestrials

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  • Frits Westra
    Forwarded by: fwestra@hetnet.nl (Frits Westra) URL: http://www.100megsfree4.com/farshores/ufolaset.htm Original Date: Thu, 28 Feb 2002 18:08:49 -0500
    Message 1 of 1 , Mar 1, 2002
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      Forwarded by: fwestra@... (Frits Westra)
      URL: http://www.100megsfree4.com/farshores/ufolaset.htm
      Original Date: Thu, 28 Feb 2002 18:08:49 -0500 (EST)

      ========================== Forwarded message begins ======================

      >>>> FarShores UFONews

      Posted Feb 27.02

      Laser Search for Extraterrestrials

      A new approach to communicating with alien civilisations.

      After almost 40 years of fruitless endeavour, no great or small radio
      signals from extraterrestrial intelligence (ETI) have been found. The
      Universe appears silent even though instruments literally billions of
      times more powerful than Frank Drake's primitive one-channel radio
      telescope have come online.

      Drake was the first scientist to carry out a search for ETI with a
      radio telescope in 1960. His predictions that we would find ETI by
      the 1980s have not been realised and he has had on more than one
      occasion to revise his estimates for a successful detection. The
      reality is that the ETI search is a cosmic enterprise and we may not
      know that ETI exist for several more decades.

      This has not stopped a new group of 'young Turks' in the US and
      Australia from expanding the search to the optical region of the
      electromagnetic spectrum. The US effort includes Prof Paul Horowitz
      from Harvard University, Dr Dan Werthimer from the University of
      California and Dr Stuart Kingsley from the Columbus Optical SETI
      Observatory, while the Australian effort is led by Dr Ragbir Bhathal
      from the University of Western Sydney.

      Bhathal's experiment is the only one in the Southern Hemisphere and
      also one of the most sensitive in the world. According to Bhathal, an
      award-winning author and astrophysicist: 'If ETI are out there they
      would have surpassed the radio threshold and gone on to communicate
      with other intergalactic civilisations by laser pulses. Light waves
      carry hundreds and thousands of times more information than radio
      waves.'

      The Universe may well be radio-silent. If this is true, radio search
      strategies are in for a big surprise and all the well-laid plans for
      the construction of a large telescope array may come to nought.

      SETI first caught Bhathal's interest when he read Drake's 1960
      article on Project Ozma in the American journal Physics Today. Being
      too busy 'earning my PhD and doing real physics,' he did not give
      SETI much thought. He was more interested in working on Nobel Prize
      winner Louis Neel's theories on magnetism. His PhD days at the
      University of Queensland were 'exciting times'. His PhD supervisor
      was Prof Frank Stacey, a Fellow of the Australian Academy of Science
      and the first recipient of the Neel Medal. He set the physics
      community agog with his ideas on the existence of a fifth force, but
      several years of searching failed to find it.

      Bhathal's interest in SETI was revived in 1996 when, out of
      curiosity, he attended a bioastronomy conference in Capri and heard
      the inventor of the laser and Nobel Prize winner, Charles Townes,
      talk about optical SETI and the possibility of ETI using lasers for
      intergalactic communication. Most of the participants were sceptical
      about what Townes was telling them and did not take him very
      seriously, but Bhathal was sufficiently impressed with Townes' talk.
      On returning home to Sydney he began his own investigations.

      He was surprised to find that not much work had been done in optical
      SETI. He organised an international conference on SETI and Society at
      the University of Western Sydney in 1998 and launched his own optical
      SETI project.

      The idea of optical SETI is not new. In the 19th century the European
      mathematician Karl Gauss proposed the use of mirrors to send light
      messages to aliens on the Moon. He remarked that if we could get in
      contact with the aliens on the Moon 'it would be a discovery greater
      than that of America'.

      Graham Bell, the inventor of the telephone, had in fact used a light
      beam to transmit messages. Called the photophone, he said that it was
      his greatest invention. However, since he used ordinary light it
      suffered from dispersion and scattering in the atmosphere and never
      saw the light of day.

      The invention of the laser by Charles Townes in the 1960s provided an
      extremely narrow and sharp beam. This property of the laser threw
      open the possibility of using lasers to communicate. This led
      Schwartz and Townes to suggest in a long-forgotten article in Nature
      that lasers could be used for interstellar communication rather than
      radio waves. The idea did not get off the ground because in the 1960s
      lasers were considered novelties and their power was small.

      In contrast radio technology, which had a head start of several
      decades, was relatively mature. Thus, the scientific community
      concentrated the search for ETI in the radio region of the
      electromagnetic spectrum, especially at the special emission
      frequency (1.4 gigahertz) of neutral atomic hydrogen - called the
      '21cm line' after its wavelength.

      In February 2001, Bhathal published an article in the British journal
      Astronomy & Geophysics in which he made a case for carrying out
      optical SETI. He said that 'Moore's Law doubling of laser
      technology over the last 40 years has seen laser power rise
      exponentially from the milliWatt lasers used in undergraduate
      laboratories to megaWatt lasers in industry'. For instance, the
      National Ignition Facility in the US has produced laser powers in the
      terraWatt range (1012 Watts), albeit for short periods. These
      developments, Bhathal argued, give tremendous credence to the search
      for ETI signals in the form of nanosecond laser pulses.

      We already have the technology that can produce extremely short laser
      pulses of petaWatts (1015 Watts). If one couples this to a large
      optical telescope like the 10-metre Keck, which is used like a
      searchlight mirror, we have an efficient system of directing
      nanosecond laser pulses at other interstellar civilisations.

      Laser light produced like this and directed towards the solar system
      would easily outshine the light from the star from which the light
      originated. According to Bhathal, the nanosecond laser pulse would
      appear about 5000-7000 times brighter than the background light from
      the ETI star. This fact is independent of distance, since both the
      laser light and the light from the ETI star will diminish at about
      the same rate with distance.

      The other advantage, according to Bhathal, is that no magic
      frequencies are involved in an optical search, unlike the radio
      search at the 21 cm line. 'We don't have to guess the ETI laser
      wavelength,' he said. The stark difference between signal and
      starlight will show up in any search that uses a broadband 'white
      light' detector, such as a photomultiplier tube.

      There are a number of other reasons for searching for ETI signals in
      the optical region. It is well-known from observations that the
      ionised hydrogen in interstellar medium causes smearing and
      degradation of transmitted radio signals. While dispersion broadens
      radio pulses, it is negligible at optical frequencies. The
      transmitted beams from optical telescopes are sharper and narrower
      than their radio counterparts.

      The discovery of several other lines of astronomical interest led
      Townes to question the superiority of the 21 cm line as the only
      wavelength at which ETI will be transmitting signals. Kingsley
      further questioned the almost religious use of the 21 cm line as the
      favoured search frequency.

      Together with Bhathal, Kingsley organised an international conference
      on optical SETI in January 2001. It was held in Silicon Valley,
      America's centre of new and exciting ideas and endeavours. Attended
      by more than 100 SETI researchers and keynoted by Townes, it marked
      the rise of optical SETI as a major new force in the search for ETI.

      One of the great advantages of doing optical SETI, according to
      Bhathal, is that 'it does not require complicated equipment and
      computational power as compared with the radio search'. All that is
      required is a pair of extremely fast photon-counting detectors wired
      up in coincidence mode. This is similar to the coincidence techniques
      used in nuclear physics, where two detectors send an alert when they
      receive a signal at exactly the same moment. Very fast
      photon-counters have come on the market only recently, enabling
      optical SETI to take off.

      Bhathal's search strategy is to look for nanosecond laser pulses
      within a volume of 100 light years. These are likely to be deliberate
      signals from ETI to us, rather than 'noise' generated by an advanced
      civilisation communicating with itself.

      There are about 1000 stars within Bhathal's search range. Assuming
      that an ETI civilisation targets one star after another and fires a
      laser pulse at perhaps 10 stars per second, then this civilisation
      could hit all Sun-like stars every 100 seconds. Bhathal thus spends a
      few minutes on each star and revisits the stars on his nightly run.

      He has designed very fast and extremely sensitive detector systems
      that he attaches to two telescopes separated by a few metres at his
      OZ OSETI observatory at the University of Western Sydney in
      Campbelltown, a semi-rural suburb about 60 km from the heart of
      Sydney. Bhathal says that 'most Campbelltownians switch off their
      lights and are asleep by 10 pm, thus leaving the night sky quite
      dark'. Even so, light pollution does not cause a problem with optical
      SETI. In fact, Kingsley says that optical SETI can be carried out
      during the day with suitable filters.

      In Bhathal's set-up, light from the telescopes is split by
      beam-splitters and falls on very fast photomultiplier tubes wired in
      coincidence mode to reject any false signals. He uses two telescopes
      to ensure that the system is not bugged by false hits during an
      observation run. His system is different from that of his American
      counterparts and is much more sensitive to ETI signals. By keeping
      track of the light flash intensity when the paired detectors respond
      simultaneously, it is possible to know whether ETI has sent a signal.
      Distant lightning flashes or static electricity or other extraneous
      fast flashes of light do not pose a problem for Bhathal's detector
      system since these flashes are not in the nanosecond range.

      After almost a year's observations of 100 Sun-like stars and 15
      globular clusters, no evidence of intentional laser signals have been
      found. So what are his plans for the future? Bhathal says he will
      continue to monitor another 2000 stars, 30 globular clusters and a
      few galaxies. He has also drawn up plans for the construction of a
      1-metre dedicated optical SETI telescope to carry out an all-sky
      survey. The wide-field telescope will carry out a meridian transit
      survey in which the night sky will drift through the field of view of
      his stationary telescope. 'The telescope will be used as a light
      bucket and it will not need to be highly accurate,' he said. 'A few
      arcminutes would be sufficient for the purposes of the project.' The
      whole southern sky would be covered in about 250 clear nights.

      In case he does discover a signal he has a bottle of champagne in his
      observatory to celebrate the event.

      Story originally published by:
      Australasian Science [March] | David Davids - Feb 26.02

      All Copyrightsco are acknowledged.
      Material reproduced here is for
      educational and research purposes only.

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